Page 138 - Biology_F5

Comparative studies of natural groups of organisms

Adaptations of Rhizopus to their mode
of life Activity 3.3: Observation of Rhizopus
Members of Rhizopus are saprophytic, and
can grow and survive on various organic Materials
substrates including bread, mature fruits, Bread, petri or dissecting dishes, hand
and vegetables. They are able to acclimatise lens or light microscope, and slides
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themselves to their environment due to the
presence of the following adaptive features: Procedure
(a) Pressure in columella makes the (a) Take one slice of bread from a dish.
sporangium burst to release haploid (b) Leave it exposed on a bench for five
spores. Each individual spore upon to seven days, until black hair-like
falling on conducive environment can structures appear on the slice.

germinate to a new hyphae body. These (c) Use a hand lens or a light microscope
asexual spores are produced in large to observe the specimen on the slice.
quantities; even in harsh conditions Carefully, observe the upright hyphae
when the environment is dry, they with black spherical structures at their
ensure a quick spread of the species. tips.

(b) They have rhizoids for anchorage on the Questions
substrate and absorption of nutrients. 1. Describe the structure of the

(c) Their hyphae show chemotropism; observed specimen.
in response to the digested food 2. Identify the specimen by its
substances. common name.

(d) They produce thick-walled resistant,
dormant zygospore. This enables the Phylum Ascomycota
spores to withstand unfavourable and These are ascocarp forming fungi such as
adverse conditions. yeasts (Saccharomyces), Aspergillus, and
(e) The wall of sporangium is so brittle that Penicillium. The ascocarp are cup-like
it easily breaks off to release the spores structures containing small sacs which
and ensure their multiplication. produce spores known as ascospores,
resulting from sexual reproduction. Besides
(f) Under asexual reproduction, they sexual spores, ascomycetes produce asexual
produce large number of spores to spores called conidia, which develop at
ensure their survival. the tips of specialised hyphae called

(g) The spores are small and very light, conidiophores. This is the most diverse
and the sporangia are raised up to aid group with about 30,000 described species.
dispersal of spores by wind. Organisms in this phylum form many
colourful cup-shaped growths called morels
on decaying logs of trees, fruits, crops,

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